1. Field of the Invention
This invention relates to the field of suspensions for disk drives. More particularly, this invention relates to the field of a disk drive suspension having an offset swage hub hole.
2. Description of Related Art
In disk drives such as magnetic medium hard disk drives, a read/write data transducer head is typically carried on head slider, which is mounted a suspension at a distal end of the suspension for writing data to, and reading data from, a recording medium such as a spinning magnetic disk platter. The suspension is typically affixed to an actuator arm by swaging, the actuator arm being carried on an E-block which carries a number of actuator arms each having their own associated suspensions affixed thereto. The E-block is moved by a voice coil motor in order to position the read/write head over the proper place on the spinning magnetic disk platter. Each suspension typically has a base plate, the base plate having a swage hub by which the suspension is swaged to the actuator arm. This arrangement and the swaging process is discussed more fully in U.S. Pat. No. 8,049,995 to Ee et al. and U.S. Pat. No. 6,215,624 to Summers, both of which are assigned to the present applicant. FIG. 1 shows a representative prior art suspension 10 having a load beam 12, a spring or spring region 13, and a base or base plate 20 having a swage boss tower or swage hub 22. The swage hub 22 is inserted through swage hole 15 in actuator arm 14, and a swage ball (not shown) is then passed through swage hub 22 in order to securely swage suspension 10 to actuator arm 14.
The angle of the suspension arm relative to the actuator arm, or the pitch static attitude (PSA) and the roll static attitude (RSA) after swaging and before adjustment are highly sensitive to small irregularities in the suspension and actuator arm and in the swaging process itself, and particularly in the swage hub dimensions. This sensitivity leads to undesirable variations in the final position of the transducer head at the end of the suspension arm relative to the recording medium platter.
U.S. Pat. No. 9,013,833 to Aparimarn suggests using a non-circular swage hole, such as an elliptical or oval shaped, swage hole or boss tower outside surface, or both, in order to increase compression between the swage boss tower and the actuator arm aperture in the roll direction more than in the pitch direction. However, such non-circular features are difficult to manufacture particularly within tight tolerances, and present additional difficulties for deswage/rework.